Intraoperative computed tomography navigation for transpedicular screw placement in posterior instrumentation and correction of adolescent idiopathic scoliosis

Abstract

Background: Intraoperative computed tomography (iCT) navigation produces high resolution real-time 3-dimensional images, which can be obtained after the well-prepared surgical field of posterior spinal elements is scanned by the iCT. There is a paucity of studies reporting the feasibility of the iCT navigation system integrated into posterior instrumentation and correction for adolescent idiopathic scoliosis (AIS). Purpose: This study is to evaluate the safety and accuracy of transpedicular screws (TPS) placement in AIS using the iCT navigation. Methods: We performed a retrospective review of records of the Spine Operation Registry at the authors’ institution to identify AIS patients who underwent correction with posterior pedicle screw instrumentation via the iCT navigation from year 2010 to 2014. Results: A total of 17 AIS patients underwent correction with posterior instrumentation via iCT navigation. A total of 245 screws including 175 thoracic screws and 70 lumbar screws were placed. The mean estimated blood loss was 718 ml (range, 350–1,500 ml) and the average operative time was 266 min (range, 150–420 min). The mean dose of patient radiation exposure was 20.1 mSv (range, 13.1–30 mSv) and the mean radiation dose per single level exposure was 1.9 mSv (range, 1.2–2.7 mSv). The average Cobb angles of major curve before surgery, in the immediate postoperative period, and at the most recent follow-up were 53.2 degrees, 16.5 degrees, and 17.7 degrees, respectively. The average correction rate was 67% (range, 50%–82%) with an average of 10.7 fused levels (range, 8–14 fused levels). A total of 236 screws (96%) were positioned in the pedicle without cortical breach, including 167 thoracic screws (95%) and 69 lumbar screws (99%). There were 90 wellpositioned screws (96%) on the concave side and 77 well-positioned screws (95%) on the convex side of the thoracic curves. There were 32 wellpositioned screws (100%) the concave side and 37 well-positioned screws (97%) on the convex side of the lumbar curves. Breach grade 1 occurred in one thoracic pedicle screw and one lumbar pedicle screw, and breach grade 2 occurred in seven thoracic pedicle screws. All screws with breach grade 2 were removed. The TPS removal rate was 3% (7/245) without any neurovascular sequela. Conclusion: TPS placement using the iCT navigation system resulted in 96% accuracy in posterior instrumentation and correction of AIS. A malpositioned pedicle screw could be immediately removed during real-time assessment of the TPS position, and no secondary operation was required.